Double circulation, the structure of the heart, arteries veins and capillaries, the four components of blood, and treatments for coronary heart disease.
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1.What kind of circulatory system do humans have?
A double circulatory system.
2.Describe the two circuits of a double circulatory system.
One carries deoxygenated blood from the heart to the lungs and oxygenated blood back. The other carries oxygenated blood from the heart to the body and deoxygenated blood back.
3.What is the advantage of a double circulatory system?
Blood returns to the heart before going to the body, so it can be pumped out at high pressure. That means faster flow and quicker delivery of oxygen.
4.Name the four chambers of the heart.
Right atrium, right ventricle, left atrium, left ventricle.
5.Which side of the heart handles deoxygenated blood?
The right side.
6.Which blood vessel brings deoxygenated blood into the heart?
The vena cava, into the right atrium.
7.Which vessel carries blood from the heart to the lungs?
The pulmonary artery.
8.Which vessel returns blood from the lungs to the heart?
The pulmonary vein.
9.Which vessel carries oxygenated blood from the heart to the body?
The aorta.
10.Why is the wall of the left ventricle thicker than the right?
It has to pump blood all the way around the body, so it must generate a much higher pressure. The right ventricle only pumps to the lungs.
11.What do the valves in the heart do?
They stop blood flowing backwards, keeping it moving in one direction.
12.Where is the natural pacemaker and what does it do?
A group of cells in the right atrium. It sends out electrical impulses that set the resting heart rate.
13.What is an artificial pacemaker?
A small electrical device implanted under the skin to correct an irregular heartbeat.
14.Describe the structure and function of arteries.
Thick walls with muscle and elastic fibres and a narrow lumen. They carry blood away from the heart at high pressure.
15.Describe the structure and function of veins.
Thin walls, a wide lumen and valves. They carry blood back to the heart at low pressure.
16.Describe the structure and function of capillaries.
Walls only one cell thick and a very narrow lumen. Substances diffuse in and out of the surrounding cells here.
17.Why do veins need valves but arteries do not?
Blood in veins is at low pressure and could flow backwards. Blood in arteries is at high pressure, which keeps it moving forwards.
18.How do you calculate the rate of blood flow?
rate of flow = volume of blood divided by the time taken.
19.Name the four components of blood.
Plasma, red blood cells, white blood cells and platelets.
20.What does plasma do?
It is the straw-coloured liquid that carries the blood cells and transports dissolved substances such as carbon dioxide, urea, glucose and hormones.
21.What is the function of red blood cells?
They carry oxygen from the lungs to the body tissues.
22.Give two adaptations of red blood cells.
A biconcave disc shape giving a large surface area for absorbing oxygen, and no nucleus so there is more room for haemoglobin.
23.What does haemoglobin do?
In the lungs it binds with oxygen to form oxyhaemoglobin. In body tissues the reaction reverses and oxygen is released.
24.What do white blood cells do?
They defend against pathogens by engulfing them, by producing antibodies, or by producing antitoxins.
25.What are platelets and what do they do?
Small fragments of cells with no nucleus. They help the blood clot at a wound.
26.Why is blood clotting important?
It stops blood loss and seals the wound so pathogens cannot get in.
27.What are the coronary arteries?
The vessels that branch off the aorta to supply the heart muscle itself with oxygenated blood.
28.What causes coronary heart disease?
Layers of fatty material build up inside the coronary arteries, narrowing them and reducing the flow of blood, so the heart muscle receives less oxygen.
29.What is a stent and how does it help?
A mesh tube inserted into a narrowed artery to hold it open, so blood can flow through normally again.
30.What are statins and what do they do?
Drugs taken to reduce the amount of cholesterol in the blood, which slows the rate at which fatty material builds up in the arteries.
31.Give one advantage and one disadvantage of statins.
They reduce the risk of heart attacks and strokes, but they have to be taken long term and can cause side effects such as muscle pain.
32.How can faulty heart valves be treated?
They can be replaced with a biological valve from an animal or a human donor, or with a mechanical valve.
33.What can be done if a heart fails completely?
A heart transplant, sometimes with a transplanted lung. An artificial heart can keep a patient alive while waiting, or give a heart time to recover.
34.Give a disadvantage of an artificial heart.
Blood does not flow through it as smoothly, so clots are more likely. Patients must take drugs to thin the blood, which brings a risk of bleeding.
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